1. Field of the Invention
The present invention relates to a method for manufacturing an electronic device having a hollow package and suitable for use in overcurrent-protection devices, and particularly to an electronic device, which houses an overcurrent-protection device.
2. Description of the Prior Art
Overcurrent-protection devices are often installed in electronic equipment to prevent electronic components therein from being damaged due to overcurrents or miss-connection of power sources in reverse. Generally, these overcurrent-protection devices are formed of a fuse element designed to melt just before the current becomes large enough to damage the electronic components. Conventional fuse elements of old days were sealed in a glass tube. Newly conventional fuse elements were sealed in resin, that is, for example, disclosed in Japanese laid-open utility model publication 57-46615.
FIG. 1 shows a conventional resin-sealed overcurrent-protection device. The device includes a pair of leads 1 and 2; a fine wire 3 made of gold, silver, or the like and connected to the leads 1 and 2 by wire bonding; and a nonflammable resin 4 surrounding the leads 1 and 2 and housing the fine wire 3 therein. The resin 4 comprises, for example, a silicon resin or the like and is formed by molding. The fine wire of metal 3 has a diameter of approximately 30 um and serves as a fuse element, in which the diameter of the wire is determined by a relationship between the diameter and it""s cutoff or fusing current.
However, although the resin 4 is classified to be nonflammable, it can emit sparks and smoke or change color due to heat generated when the fine wire 3 is melted off by overcurrents. When the element designed to protect equipment thereby emits sparks or smokes, it may affect the equipment in an adverse manner, and reduce reliability thereof.
Widely varied types of portable electronic equipment such as mobile telephones are powered by batteries in portable use, and it is necessary to implement measures for protection from miss-connection of the batteries in reverse during installation thereof. In such equipment, an overcurrentxe2x80x94protection element is essential. However, by employing these conventional elements in portable electronic equipment, it tends to make the equipment larger, while the equipment is required to be lighter, thinner, and smaller all around.
In view of the foregoing, it is an object of the present invention to provide an electronic device and a method for manufacturing an electronic device such as a small overcurrent-protection device that does not emit sparks or smoke or cause the device to change color or shape when the fuse element melts.
To achieve the object of the present invention, there is provided a method for manufacturing an electronic device, comprising: preparing a common substrate having a plurality of element mounting sections; fixing an element in each of the element mounting sections; sealing the element mounting sections in a hollow space by using a common cover member; and separating the plurality of element mounting sections into individual electronic devices.
According to a second aspect of the present invention, there is provided an electronic device, comprising: a substrate having first and second main surfaces; at least a pair of electrodes formed on the first main surface of the substrate; a fuse element connecting each of the pair of electrodes; a cover member hermetically sealing the fuse elements in a hollow space; and external connection terminals formed on the second main surface of the substrate and electrically connected to each one of the electrodes.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.